1. Field of the Inventive Concepts
The presently claimed and disclosed inventive concepts relate generally to metal matrix composites, and more particularly, to metal matrix nanocomposites having a bimodal microstructure and to methods of making bimodal metal matrix nanocomposites.
2. Brief Description of Related Art
Particle reinforced metal matrix composites (MMCs) have gained extensive attention for structural applications because of their high specific strength and elastic modulus, near-isotropic properties, and excellent high-temperature creep resistance. In particular, magnesium-based metal matrix composites (MMMCs) have attracted increasing interest due to the fact that magnesium is the lightest metallic material. However, the significantly reduced ductility of micrometer-sized particle reinforced MMMCs has limited their application.
Consequently, magnesium-based metal matrix nanocomposites (MMMNCs) have been developed, with the assumption that the mechanical properties of MMCs could be further enhanced while retaining ductility by using nano-sized reinforcements. Powder metallurgy, disintegrated melt deposition (DMD), ultrasonic cavitation based casting, and friction stir processing have been utilized to manufacture MMMNCs which show a high degree dispersion and uniformity of the reinforcement. It has been demonstrated that these processes can produce magnesium nanocomposites containing less than 1 volume percentage ceramic nanoparticles which exhibit good mechanical properties while retaining ductility. However, these processes are complex and costly, and the mechanical properties of the magnesium nanocomposites containing less than 1 volume percent of ceramic nanoparticles are still not good enough for many applications.
It would be advantageous to develop metal matrix nanocomposites and MMMNCs having improved mechanical properties while retaining ductility. It would also be advantageous if a low cost process could be developed to produce metal matrix nanocomposites including MMMNCs containing a high volume fraction of nano-sized ceramic particles.